Orky escorts vs ordinance/Imperial Escorts Pt. 1 (the death of the escorts!)
Taking an Onslaughts stats, we have it become subject to attack by both AC and Bombers.
1 ac counter has a 41.6% chance of killing an onslaught, 2 have a 90% chance of killing it. For a sword class escort (the closest comparable example) 1 ac would kill a sword 20.8% of the time, and two would only have a 60.6% chance.
1 bomber has a 33.6% chance of killing it, 2 would have 58.3% chance. Compared to the sword 1 would have a 10.5% chance, 2 would have a 26.8% chance.
1 torp (from the front, then the sides) will kill an ork 8.8%% of the time, whereas from the side 25%, a sword would die from the front/sides 8.325% of the time.
Of course making Ac only effective on a 4+ as proposed would change this slightly:
1 ac=25% chance of killing onslaught, 2 have 56.25%,, almost the same as bombers. Similarly with the sword; 12.5%, and 37.5% respectively.
Now as more evidence for a points reduction in ork escorts, I guess I'll use my previous formula to compare the onslaught with the sword. Noting an account in survivability for the differences in armor, counting side/rear once.
a sword is 94.62% as survivable vs direct fire, counting for points. Now if we include what we know now about ordinance we can change this to: 125.6% survivability vs all weapons.
Also noting the difference in weapon strengths, an onslaught only has 76.9% as much firepower as the adjusted sword. For now we won't note the areas of attacks, as the sword will neatly double the onslaught in that. And as Sigoroth pointed out, the rear stuff isn't as important as what is in front of you.
So here we note that an onslaught is about 78% as effective as a Sword. Noting that comparing between different fleets is hard, because playstyle has a lot to do with it, but imperials are the closest. In this scenario, an onslaught should cost around 28 points, which is accurate with our comparison to the brute, which pegged it at 30. Now if we did some of the same things as our previous solution of increasing the onslaughts fp to d6+1 and reducing it to 35, then it would be about worth 90% of a sword, much more reasonable.